A thin film transistor employing an oxide semiconductor as an active layer may be processed at a low temperature and with low costs, and also obtain a high mobility characteristic, thereby attracting attentions as a backplane device of an active drive-type display. Recently, technologies of forming source and drain electrodes so as to be self-aligned by using a gate electrode as a mask in manufacturing an oxide semiconductor thin film transistor have been suggested.
FIG. 1 is a configuration diagram of a thin film transistor in the related art.
In the related arts, source and drain electrodes are formed by doping hydrogen in source and drain regions or performing a plasma treatment on the source and drain regions. However, in a case where the aforementioned methods are performed, as a subsequent process, such as a heat treatment, is performed, a doping effect gradually deteriorates, so that there is a possibility in that an operation characteristic of a transistor will deteriorate. In a case where an element, other than hydrogen, is doped, an activation temperature of a dopant is high, so that a problem may occur in that it is difficult to apply the method to a substrate, such as glass or plastic, having a poor heat resistance characteristic.
In order to implement a high resolution display, a region occupied by a thin film transistor within one pixel may be decreased by minimizing a size of the thin film transistor, and according to the related art, it is necessary to form the source and drain electrodes through the doping and then connect a separate wiring electrode to source and drain electrodes of the thin film transistor for an electronic circuit configuration. In this case, as illustrated in FIG. 1, in order to form an electrode connected to the source and drain regions, a margin necessary for mask alignment and a margin for a length and a width of a contact hole are generated, and as a result, there is a problem in that widths of the source and drain regions are increased.